1. Field of the Invention
The present invention relates to a semiconductor device having switching function such as IGBT (Insulated Gate Bipolar Transistor), GCT (Gate Commutated Turn-off Thyristor) or GTO (Gate Turn-off Thyristor).
2. Description of the Background Art
FIG. 8 is a cross section showing a structure of a conventional reverse conducting GTO. Here, there will be explained below GTO as an example of a semiconductor device having a switching function. Normally, the reverse conductive GTO is constituted so that a GTO area is connected to a free wheeling diode area in antiparallel and these areas are integrated in one semiconductor substrate.
In the conventional reverse conducting GTO, a P layer 602, and an NE layer 603 are diffused on a semiconductor substrate N-layer 601 made of silicon or the like in order from a cathode side in a GTO area 620. Similarly an N+ layer 604 and a PE layer 605 are diffused in order from an anode side. In a diode area 621, the P layer 602 is diffused on the semiconductor substrate Nxe2x88x92 layer 601 made of silicon or the like from the cathode side, and the N+ layer 604 and an N++ layer 606 are diffused in order from the anode side.
In addition, this reverse conducting GTO has a cathode electrode 607 and a gate electrode 608 in the GTO area, a cathode electrode 609 in the diode area and an anode electrode 610 in the whole area. In a separating area which separates the GTO area 620 from the diode area 621, an etching section 611 is provided on a portion of the P layer 602 which remains on the Nxe2x88x92 layer 601 after a diffusion area of the P layer 602 of about 90 xcexcm is etched down by about 60 xcexcm, and the width A of the etching portion is about 5 mm. Resistance of 300 to 500xcexa9 is provided between the GTO area 620 and the diode area 621 and they are separated by the etching area with the width A of about 5 mm. Paying attention to thermal resistance, thermal resistance is generated on the surface of the GTO area 620 at the time of operating GTO, and on the surface of the diode area 621 at the time of operating diode.
Further, relating techniques are disclosed in Japanese Patent Application Laid-Open Nos. 9-191110 (1997) and 2-309676 (1990). Japanese Patent Application No. 9-191110 (1997) discloses an insulating gate bipolar transistor containing a diode. In this transistor, a cathode electrode and a collector electrode are integrated, and an anode electrode and an emitter electrode are integrated so that a size of the whole transistor is reduced.
Japanese Patent Application Laid-Open No. 2-309676 (1990) discloses a reverse conducting-type insulated gate bipolar transistor. In this transistor, a source of IGBT and an anode of a diode are formed by one electrode, and a collector of IGBT and a cathode of the diode are formed by one electrode.
In the conventional reverse conducting GTO (FIG. 8), since the GTO area 620 and the diode area 621 are separated by high resistance, the separating area is required. Moreover, in this reverse conducting GTO, since thermal resistance is generated on the surface of the GTO area 620 and on the surface of the diode area 621, there arises a problem that the thermal resistance in the reverse conducting GTO is high. Further, as for both the diodes disclosed in Japanese Patent Application Laid-Open Nos. 9-191110 (1997) and 2-309676 (1990), a switching element and the diode use one electrode so that the whole diode becomes compact. However, a separating area which separates the switching element area from the diode area is required. There arises a problem that an actual operating area is reduced due to this separating area and thus a performance of a semiconductor device is deteriorated.
The present invention is devised in order to solve the above problems, and it is an object of the present invention to provide a semiconductor device in which a switching ability and a diode ability can be used properly in a regular direction and a reverse direction in one structure, thereby increasing a surface area of a chip and reducing thermal resistance, and a separating area is eliminated, thereby increasing an actual operating area.
In order to achieve the above objects, a first aspect of the invention provides a semiconductor device characterized by including: a semiconductor substrate; wherein the semiconductor includes: a first conducting-type first semiconductor layer; a second conducting-type second semiconductor layer; a first conducting-type third semiconductor layer; a second conducting-type fourth semiconductor layer; and a first conducting-type fifth semiconductor layer; a first main electrode for short-circuiting the first semiconductor layer and the second semiconductor layer; a second main electrode for short-circuit the fourth semiconductor layer and the fifth semiconductor layer; and a control electrode provided on the third semiconductor layer. The semiconductor device is characterized in that the first semiconductor layer and the second semiconductor layer form a joint, the second semiconductor layer and the third semiconductor layer forms a joint, the third semiconductor layer and the fourth semiconductor layer form a joint, and the fourth semiconductor layer and the fifth semiconductor layer form a joint.
In accordance with the semiconductor device of the first aspect of the present invention, the area having the switching ability and the area having the diode ability are provided and they commonly have the PN joint so that the surface area is increased and the thermal resistance can be reduced. Further, since an area which separates the area having the switching ability from the area having the diode ability is not provided, the actual operating area can be increased.
The semiconductor device of the second aspect of the invention, which relates to the semiconductor device of the first aspect, is characterized in that the first semiconductor layer and the third semiconductor layer are separated by the second semiconductor layer, and the third semiconductor layer and the fifth semiconductor layer are separated by the fourth semiconductor layer.
In accordance with the semiconductor device of the second aspect of the present invention, the area having the switching ability and the area having the diode ability are provided and they commonly have the PN joint so that the surface area is increased and the thermal resistance can be reduced. Further, since an area which separates the area having the switching ability from the area having the diode ability is not provided, the actual operating area can be increased.
The semiconductor device of the third aspect of the invention, which relates to the semiconductor device of the first aspect, is characterized in that the first semiconductor layer and the second semiconductor layer are exposed from a first main surface of the semiconductor substrate, and the first semiconductor layer is surrounded by the second semiconductor layer.
In accordance with the semiconductor device of the third aspect of the present invention, the area having the switching ability and the area having the diode ability are provided and they commonly have the PN joint so that the surface area is increased and the thermal resistance can be reduced. Further, since an area which separates the area having the switching ability from the area having the diode ability is not provided, the actual operating area can be increased.
The semiconductor device of the fourth aspect of the invention, which relates to the semiconductor device of the first aspect, is characterized in that the fourth semiconductor layer and the fifth semiconductor layer are exposed from a second main surface of the semiconductor substrate, and the fifth semiconductor layer is surrounded by the fourth semiconductor layer.
In accordance with the semiconductor device of the fourth aspect of the present invention, the area having the switching ability and the area having the diode ability are provided and they commonly have the PN joint so that the surface area is increased and the thermal resistance can be reduced. Further, since an area which separates the area having the switching ability from the area having the diode ability is not provided, the actual operating area can be increased.
The semiconductor device of the fifth aspect of the invention, which relates to the semiconductor device of the first aspect, is characterized in that the first conducting type is p type.
In accordance with the semiconductor device of the fifth aspect of the present invention, the area having the switching ability and the area having the diode ability are provided and they commonly have the PN joint so that the surface area is increased and the thermal resistance can be reduced. Further, since an area which separates the area having the switching ability from the area having the diode ability is not provided, the actual operating area can be increased.
The semiconductor device of the sixth aspect of the invention, which relates to the semiconductor device of the first aspect, is characterized in that the first semiconductor layer is exposed from a first main surface of the semiconductor substrate and a maximum width in a short-length direction of the exposed surface of the first semiconductor layer is not more than 100 xcexcm.
In accordance with the semiconductor device of the sixth aspect of the present invention, the effect which is similar to that of the semiconductor device of the first aspect of the invention can be obtained. Further, the maximum width in the short-length direction of the exposed surface of the first semiconductor layer is set to not more than 100 xcexcm so that the semiconductor device can be prevented from being broken due to the spike voltage at the time of the switching operation.
The semiconductor device of the seventh aspect of the invention, which relates to the semiconductor device of the first aspect, is characterized in that the first main electrode is a cathode and the control electrode is provided only on the third semiconductor layer.
In accordance with the semiconductor device of the seventh aspect of the present invention, the effect which is similar to that of the semiconductor device of the first aspect of the present invention can be obtained. Further, the area having the switching ability can be formed as GCT, GTO or the like.
The semiconductor device of the eighth aspect of the invention, which relates to the semiconductor device of the first aspect, characterized in that the first and second main electrodes are pressed by a metal plate.
In accordance with the semiconductor device of the eighth aspect of the present invention, the effect which is similar to that of the semiconductor device of the first aspect of the present invention can be obtained. Further, the structure which can be used more easily can be obtained.
The semiconductor device of the ninth aspect of the invention, which relates to the semiconductor device of the first aspect, is characterized in that a dielectric layer is provided between the control electrode and the third semiconductor layer.
In accordance with the semiconductor device of the ninth aspect of the present invention, the effect which is similar to that of the semiconductor device of the first aspect of the present invention can be obtained. Further, the area having the switching ability can be formed as IGBT or the like.
The semiconductor device of the tenth aspect of the invention, which relates to the semiconductor device of the ninth aspect, is characterized in that a portion of the control electrode is positioned on the second semiconductor layer or on the second semiconductor layer and the first semiconductor layer.
In accordance with the semiconductor device of the tenth aspect of the present invention, the effect which is similar to that of the semiconductor device of the ninth aspect of the present invention can be obtained. Further, the area having the switching ability can be formed as IGBT or the like.
The semiconductor device of the eleventh aspect of the invention, which relates to the semiconductor device of the ninth aspect, is characterized in that the first main electrode is an anode.
In accordance with the semiconductor device of the eleventh aspect of the present invention, the effect which is similar to that of the semiconductor device of the ninth aspect of the present invention can be obtained. Further, the area having the switching ability can be formed as IGBT or the like.
The semiconductor device of the twelfth aspect of the invention, which relates to the semiconductor device of the ninth aspect, is characterized in that in the case where an electric potential of the first main electrode is higher than an electric potential of the second main electrode, an electric potential of the control electrode is controlled to not more than the electric potential of the first main electrode.
In accordance with the semiconductor device of the twelfth aspect of the present invention, the effect which is similar to that of the semiconductor device of the ninth aspect of the present invention can be obtained. Further, the structural breakdown of the PN joint can be prevented in the case where a reverse voltage is applied.